Let us assume the validity of Ampère's circuital law ∮γB⋅dx=μ0Ilinked
where B is the magnetic field, γ a closed path linking the current of intensity Ilinked.
Can the Biot-Savart law B=μ04π∮Idℓ׈rr2=μ04π∫baIℓ′(t)×x−ℓ(t)‖x−ℓ(t)‖3dt
where ℓ:[a,b]→R3 is a parametrisation of a closed (or infinite) wire carrying the current I, be inferred without using Dirac's δ, by using the tools of multivariate calculus and elementary differential geometry only, at least if we assume the validity of the Gauss law for magnetism or other of the Maxwell equations? All the proofs I have found (such as this, where, as far as I understand, ∇2[μ04π∫J(r′)|r−r′|d3r′]=−μ0J(r)
is derived by using the δ) use the expression B=μ04π∫VJ׈rr2d3x
and Dirac's δ, but I wonder whether, both assuming a linear current distribution as when we use the expression of the magnetic field asB=μ04π∮Idℓ׈rr2
and assuming a tridimensional spatial current distribution, it is possible to prove the Biot-Savart law from Ampère's without the use of the δ. I heartily thank any answerer.
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